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Cape officials plead with scientists for consensus on expected rainfall

16 May 2017 - 15:13
Bobby Jordan

Picture: ISTOCK

Anxious City of Cape Town officials pleaded with scientists attending a panel discussion on the Western Cape’s dry weather to predict this year’s expected rainfall figures — and what was likely to happen in the near future.

The measured tones of several distinguished climate scientists were in stark contrast to a frantic request for help from two city officials who arrived late at Monday’s panel discussion.

"We need your help. We need a consensus from you — this is really important‚" said city official Sarah Rushmere.

"It is getting down to the point where we have to make emergency decisions. Daily we are making decisions‚" Rushmere said‚ adding that the city was facing a revolt on social media from panicked customers.

City water supply manager Barry Wood said he was also concerned about talk that the dry conditions could be linked to the El Nino weather phenomenon.

"It is this kind of information that we need to be clear on. It is a bit worrying if we look at what the weather service is saying that El Nino is establishing itself possibly quicker — that possibly has some implications for us as well‚" Wood said.

"At the end of the day, a city of 4-million people can’t run out of water. We will just have to have austerity measures‚" he said‚ adding that an additional problem was that Cape Town’s water supply system was not well-suited to "water shedding".

The officials’ comments coincided with a "critical warning" for residents to use water only for drinking‚ bathing and cooking.

Rushmere said other possible supply-mitigation measures included rebates for residents collecting their own rainwater — via rooftop tanks — and drilling additional boreholes.

Responding to the city’s concerns‚ several scientists outlined difficulties inherent in making accurate rainfall estimates. They committed to working together in a newly convened group‚ the Alliance for Collaboration and Earth Systems Science‚ to help answer some of the city’s key questions.

In a statement‚ the group said longer-term trends‚ which tended to be more reliable‚ suggested that the Western Cape was in for a dry spell.

"There is a weight of evidence provided by a large body of published research‚ adequately assessed in the most recent Intergovernmental Panel on Climate Change (United Nations) assessment‚ as well as information provided by the CMIP5 climate model archive‚ to support the reasonable expectation of a relatively drier future Western Cape by the 2030s to 2040s‚" it said.

"There is little doubt that the Western Cape needs to prepare‚ in the longer term‚ for a drier climate. Research does continue on the finer details of these long-term changes and in particular on aspects of large-scale modes of variability and mountain climate, which are relevant‚ but currently this work remains in the domain of research rather than informing decision making."

In a separate statement‚ the Council for Scientific and Industrial Research (CSIR) said unreliable rainfall predictions suggested it was safer for affected stakeholders to err on the side of caution.

"It is the experts’ view thus that the Western Cape needs to prepare for the possibility that this year’s winter season may be drier than normal‚ which may greatly exacerbate the current situation; or it may be relatively normal‚ which will fail to relieve the current situation‚" the CSIR said.